New bulk cone singularities in Vaidya-like spacetimes from large $c$ conformal blocks

TL;DR

This paper uncovers a new class of bulk cone singularities in Vaidya-like spacetimes, showing their dependence on black hole size and confirming their CFT origin via large central charge conformal blocks.

Contribution

It introduces a novel type of bulk cone singularities in Vaidya-like spacetimes and links their existence to the black hole radius relative to the AdS length.

Findings

Bulk cone singularities appear for black hole radius less than the AdS length.

A sharp transition in causal structure occurs at the black hole radius equal to the AdS length.

Large c conformal blocks reproduce the bulk singularities in the boundary CFT2.

Abstract

Bulk cone singularities are singularities in boundary two-point functions at points separated by a null geodesic in the bulk, but not in the boundary. In this work, we describe a new type of bulk cone singularities in a family of Vaidya-like spacetimes that are labeled by the radius $r_+$ of the resulting black hole. We find a sharp transition in the causal structure within this family of spacetimes at $r_+=l$, the AdS length. In particular, there are bulk cone singularities that do not exist in the $r_+>l$ case, but appear for $r_+<l$. In the case of $r_+<l$ where such singularities exist, we are able to reproduce the singularities in a CFT$_2$ calculation using large $c$ conformal blocks.